Code generation/client package(s)

At present, ThingClient instances are generated at runtime based on Thing Descriptions. This works, but doesn't allow type checking or autocompletion. My aspiration is to enable both of these, which probably requires code generation.

The way I see this working is that labthings_fastapi should provide code that will generate a client module based on a Thing subclass. This could be integrated into the build system of a Python package, such that the built package contains a client module - or even releases a second client package (without the hardware/server dependencies). This client module would include a ThingClient subclass with all the actions and properties of the Thing.

Dependencies of things on each other would ideally go via ThingClient objects, so the generated code should be able to be used for server-side DirectThingClients as well as HTTP based ThingClients.

Start by reading the existing ThingClient and DirectThingClient implementations in labthings_fastapi, along with how Thing subclasses and Thing Descriptions are represented. Define the code-generation and package-integration scope before implementation. Done should provide typed, autocompleting client classes usable for both HTTP clients and server-side dependencies.